As we study the key systems upon which our human population depends, it quickly becomes clear that water and energy are essential. Not only are they essential, but they are also inextricably linked. It takes energy to move, heat and purify water. It also takes a great deal of water to produce energy, whether it’s from hydropower or from thermal power plants, both nuclear and fossil fuel-fired.
The most prominent example of this interdependency is in agriculture, which uses enormous quantities of both energy and water. The paper industry differs from agriculture for a couple of important reasons. First, 72 percent of the fiber used in paper comes from trees which are rainfall-fed. This, in water conservation parlance, is considered green water – which is distinguished from surface and groundwater, referred to as blue water. Agriculture also depends on rainfall, but in many cases it is supplemented by a great deal of additional water via irrigation, which is why the industry is by far the largest water consumer in the nation.
Most of the water used in the paper production life cycle is used during the manufacturing process, primarily for conveyance of the fibers as they are extracted from logs as wood chips, and through the pulping process. By the same token, most of the energy used in paper-making goes into cooking the pulp, in order to remove the fibers, and drying the wet fibrous mat as it comes out of the paper machine before it is rolled up and ultimately cut into reams or converted into cardboard. According to this Energy Star report, more than $7 billion worth of energy was purchased in 2009 for the manufacture of pulp, paper and paperboard. This is primarily used as boiler fuel for both process-steam and power generation.
Of course, there is an opportunity to do things in a smarter and greener way. There is a great deal of residual biomass such as bark that could be used to produce energy. International Paper does exactly that, generating 72 percent of its energy from forest residuals. The company has also been working to improve energy efficiency, with a goal of a 15 percent reduction in purchased energy by 2020. An investment of $290 million has led to a reduction of 9 trillion BTUs per year. At current coal prices, that will pay for itself in 8 years, though if natural gas is substituted, it could take longer. Since 2010, the company has reduced its purchased energy usage per ton of paper by 3.7 percent.Click to continue reading »